Numerical analysis of flow resistance characteristics in an inclined rod bundle channel

Abstract The thermal-hydraulic characteristics of the rod bundle channel under ocean conditions have attracted much attention. In this paper, the three-dimensional CFD numerical simulation software STAR-CCM+ is used to study the frictional resistance characteristics of the rod bundle under non-vertical conditions at inclination angles of 0°, 15°, 30° and 45°, so as to provide a reference for future reactor core design of floating nuclear power plants. Using CFD, the relationship between the frictional resistance coefficient and the Reynolds Number (Re) is obtained in a wide range of Re, including the laminar regime, the transition regime and the turbulent regime. The predicted correlation results are good and have an estimated error within ±10%. The influence of the heating flux and the inlet temperature of the test bundle is considered, and a kinematic viscosity correction coefficient is introduced. Owing to the structural characteristics of the square rod bundle channel, this paper considers two different directions of tilt: rotations about an axis perpendicular to the channel faces and about an axis which passes through opposite corners of the channel. A difference in the frictional resistance coefficient between inclined and vertical conditions only occurs in the laminar flow regime, and there is no frictional resistance coefficient difference in the transition regime or the turbulent regime. Additionally, the frictional resistance coefficient is reduced considerably if the boundary layer is disturbed, due to the reversed fluid flow in the laminar regime.